1. Field of the Invention
The present invention relates to a cover plate mounted on a copier, facsimile apparatus, image scanner or similar image forming apparatus, an image scanning device, and an image forming apparatus.
2. Description of the Background Art
Generally, a cover plate for the above application includes a frame configured to cover a glass platen, a hinge openably connecting the frame to the body of an image scanning device, an elastic member affixed to the frame by, e.g., adhesive tapes, and a pressing portion (including a white sheet) adhered to the surface of the elastic member expected to face the glass platen. The cover plate is so adjusted as to bring the pressing portion into close contact with the glass platen at the time when the hinge is mounted the body.
A problem with the above configuration is that if the hinge is even slightly dislocated relative to the body, then the pressing portion fails to closely contact the glass platen over its entire area and interferes with scales mounted on the edges of the glass platen. As a result, the scales are not fully pressed at the edges of a document laid on the glass platen and cause the document to rise above the glass platen. This not only prevents the scanning device to accurately read the edges of the document, but also allows external light to enter via the resulting gaps. Such portions are printed in black in an output image.
In light of the above, Japanese Patent Laid-Open Publication No. 10-153889, for example, discloses a cover plate including an elastic member formed of, e.g., sponge and a frame to both of which planar fasteners MAGIC TAPE (trade name) available from KURARAY CO., LTD are adhered. The fasteners are positioned at four corners of the elastic member. Only if the elastic member and pressing portion are removed, the cover plate can be easily adjusted such that the pressing portion closely contact a glass platen over its entire area without interfering with scales. Such a cover plate, however, has the following problems left unsolved.
As for a document of relatively small size, for example, the pressing portion and glass platen contact each other over a large area with the result that adhesion to act therebetween during scanning due to static electricity increases. Consequently, the pressing portion and contact glass remain in close contact with each other even when the cover plate is opened after scanning, so that a force is necessary for opening the cover plate. When the cover plate is opened by a force, it lifts the document adhering to the pressing portion. If the document is shifted toward the hinge, then it is likely to be nipped between the cover plate and the body of the image scanning device and damaged thereby. Further, the above adhesion exerts a stress on the interface between the frame and the pressing portion adhered to each other because the planar fasteners are affixed to the sponge portions. The stress is apt to damage the adhered surfaces of the sponge portions.
The glass platen is usually affixed to the body of the image scanning device by, e.g., adhesive tapes. The scales are mounted to the body by screws or similar fastening means such that they are pressed by the glass platen so as to interfere with the edges of the glass platen. Therefore, if the degree of adhesion between the cover plate and the glass platen is high, then the portion of the glass platen adjoining the operator is apt to slightly rise and allows dust to enter via the resulting gap. Moreover, if the above portion of the glass platen noticeably rises, then a heavy impact is apt to act on the glass platen.
To solve the problems described above, Japanese Utility Model Publication No. 07-034425 teaches a step member positioned on a glass platen at a side opposite to a side where a fulcrum for the glass platen is positioned, thereby reducing the degree of adhesion between the glass platen and a cover plate. The step member forms a space between the glass platen and the cover plate for allowing the cover plate to be easily opened.
Japanese Patent Laid-Open Publication No. 7-128932 proposes to use a conductive sheet having a rough surface as a white sheet customarily included in the pressing portion of a cover plate. The conductive sheet protects a book document from bending and damage ascribable to the charging of the pressing portion.
Technologies relating to the image scanning device of the type described are also disclosed in, e.g., Japanese Utility Model Publication No. 4-22346 and Japanese Patent Laid-Open Publication Nos. 6-313930, 7-95368, 7-191419, 8-201935 and 10-153889.
A problem with the step member stated above is that it prevents the sheet from fully contacting the glass platen and makes pressure to act on a document uneven. Further, light entering via the gap between the glass platen and the cover plate, causing the corresponding portion to be printed in black in an output image. On the other hand, the conductive sheet intervenes between a carriage and a device frame and rolled on a take-up roller, making the construction sophisticated and increases the cost.
It is an object of the present invention to provide a cover plate capable of bringing its pressing portion into close contact with a glass platen over the entire area and reducing a stress to act on the interface between the pressing portion and a frame during opening, an image scanning device, and an image forming apparatus.
It is another object of the present invention to provide a cover plate capable being easily opened while reducing an impact to act on a glass platen, an image scanning device, and an image forming apparatus.
A cover plate for a document scanning device or an image forming apparatus of the present invention includes a frame connected to the body the image scanning device or that of the image forming apparatus. The frame is openable away from a glass platen and divided in a direction perpendicular to the opening/closing direction. A pressing portion presses the document laid on the glass platen. Mounting/dismounting members allow the pressing portion to be selectively mounted to or dismounted from the frame. An elastic member is included in the pressing portion and includes a sheet member mounted thereon and divided into a plurality of parts and configured to contact the document.
An image scanning device and an image forming apparatus each using the above cover plate are also disclosed.